Polarisation Contents: EM Waves Polarisation angle Polaroid filters Brewster’s angle.

PolarisationContents:

•EM Waves•Polarisation angle•Polaroid filters•Brewster’s angle

Concept of polarization:

Demo - Spring

Plane Polarized light:

Io – incident intensity (W/m2)

Demo two polarizers

More than one polarizer:I = Iocos2

Io – incident intensity of polarized lightI – transmitted intensity (W/m2) – angle twixt polarizer and incident angle of polarization

Demo two polarizers

Io½Io (½ Io)cos2

Two polarizers are at an angle of 37o with each other. If there is a 235 W/m2 beam of light incident on the first filter, what is the intensity between the filters, and after the second?

I = Iocos2After the first polarizer, we have half the intensity:I = 235/2 = 117.5 W/m2

and then that polarized light hits the second filter at an angle of 37o:I = (117.5 W/m2) cos2(37o) = 74.94 = 75 W/m2

Brewster’s angle:•non-metallic surface•reflected light polarized parallel to surface.

In generaln2 = tann1

For air (n1 = 1.00) to something:n = tan

demo – small polarizers

Polarization1 | 2

TOC

I = ?, Io = 120. W/m2, = 21.0o

I = 104.58 W/m2

105 W/m2 W

120. W/m2 of vertically polarized light goes through a filter that makes an angle of 21.0o with the vertical. What is the transmitted intensity?

I = Iocos2

I = 80.0 W/m2, Io = 120. W/m2, = ? = 35.26o

35.3o W

120. W/m2 of vertically polarized light goes through a filter that makes some angle with the vertical such that only 80.0 W/m2 are transmitted. What angle does the filter make with the vertical?

I = Iocos2

After the first filter, we are down to 250 W/m2, Then we use the formula I = Iocos2 = (250 W/m2)cos(68.0o)2 = 35.08 W/m2.

35.1 W/m2 W

500. W/m2 of UNpolarized light goes through a vertically polarized filter, and then through one the makes an angle of 68.0o with the vertical. What is the transmitted intensity?

I = Iocos2

n = 1.33, = ? = 53.06o

53.1o W

What is Brewster’s angle from air to water? (n = 1.33)

n = tan

n = ?, = 67.5n = 2.420

2.420 W

What is the index of refraction of a substance that has a Brewster’s angle of 67.55o?

n = tan

Demos

• Optical activity

• Light Show

• Stress and Activity

• Birefringence